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August 22, 2012

Compared to a planet, the asteroid Vesta is tiny — only about 300 miles across. Yet Vesta more closely resembles a planet than it does any of its fellow asteroids. Like Earth and the other rocky planets, it has a core of iron and nickel, surrounded by a thick mantle of dense rock, topped by a crust of lightweight rock.

That picture was confirmed by a spacecraft named Dawn. It’s been orbiting Vesta for more than a year. From its findings about the asteroid’s composition and structure, scientists have put together a profile of Vesta’s history.

Vesta formed millions of years before Earth did — not long after the Sun itself was born. Heat from the decay of radioactive elements melted the newly formed asteroid, allowing denser material to sink to the center and lighter material to float to the top. Many small bodies with the same layered structure probably were born along with Vesta. But most of the others are gone — they merged to form planets, they were kicked out of the solar system by the giant outer planets, or they broke apart in big collisions.

Carol Raymond is a Dawn mission scientist:

RAYMOND: We now know that Vesta is the only intact layered building block surviving from the very earliest days of the solar system. Vesta is special because it survived the intense collisional environment of the main asteroid belt for billions of years, allowing us to interrogate a key witness to the events at the very beginning of the solar system.

More about Vesta tomorrow.

Script by Damond Benningfield, Copyright 2012


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